To_timestamp vs. to_date when forcing native SQL

Question

Hello!
I was recently encountering performance problems when querying on dates, and found some useful help on this forum. The suggestion I took was to set the <uses-native-sql> element to true in my sessions.xml file. This caused TopLink to use the native "to_date()" syntax instead of the generic "ts{}" syntax.
My query went from taking several minutes to taking a matter of seconds. So far, so good.
Recently, we upgraded from TopLink 9.0.4 (build 031126) to TopLink 9.0.4.5 (build 040930). Now, when I examine the generated SQL, I see that TopLink is using the native "to_timestamp()" syntax which once again slows my query to a crawl.
Any thoughts on a way around this issue? Is there a way to force TopLink to use the to_date() syntax for my particular Expression query?
We upgraded TopLink for specific reasons, so reverting to the prior version is not even a short-term work-around.
Other specifics:
* Our database is Oracle Database 10g Enterprise Edition Release 10.1.0.3.0.
* The database field being queried is defined as a Date in the schema.
* We are using version 9.0.1.5.0 of the Oracle drivers.

Answer 1

Mark,
This is the default behavior for java.sql.Timestamp and java.util.Date in TopLink for Oracle9Platform. The reason is that java.sql.Timestamp and java.util.Date have millseconds and TO_TIMESTAMP would preserve that.
To get TO_DATE, by default the java type needs to be java.sql.Date for Oracle9Platform.
If you care about the date only, I have two suggestions.
1. Use TypeConverstionMapping.
TypeConversionMapping dateMapping = new TypeConversionMapping();
dateMapping .setAttributeName("StartDate");
dateMapping .setFieldName("START_DATE");
dateMapping .setAttributeClassification(java.sql.Timestamp.class);
dateMapping .setFieldClassification(java.sql.Date.class);
2. Change java type from java.sql.Timestamp or java.util.Date to java.sql.Date.
If you want the time portion as well, you can subclass from Oracle9Platform and replace appendTimestamp with
protected void appendTimestamp(java.sql.Timestamp timestamp, Writer writer) throws IOException
if (usesNativeSQL()) {
int seconds = (timestamp.getHours() * 3600) + (timestamp.getMinutes() * 60) + timestamp.getSeconds();
java.sql.Date date = new java.sql.Date(timestamp.getYear(), timestamp.getMonth(), timestamp.getDate());
writer.write("to_date('" + date + " " + seconds + "','yyyy-mm-dd sssss')");
} else {
super.appendTimestamp(timestamp, writer);
Shannon